Curable silicone compositions that cure by a hydrosilylation reaction are used as, for example, protective agents, coating agents, lens molding materials, and light-reflecting materials for optical semiconductor devices, for example, photocouplers, light-emitting diodes, and solid-state imaging devices. Among these, the compositions used as light-reflecting materials can be exemplified by a resin composition for a mounting package that incorporates an optical semiconductor element, wherein this resin composition comprises a white pigment, a platinum-type catalyst as a curing catalyst, and a thermosetting addition-reacting silicone resin that has a structure in which vinyl groups or allyl groups, and hydrogen atoms are directly bonded to silicons (refer to Japanese Unexamined Patent Application Publication (hereinafter referred to as “Kokai”) 2009-21394; and by an addition-curing silicone resin composition that has an average visible light reflectance post-cure of at least 80% and that comprises a vinyl-functional organopolysiloxane having a weight-average molecular weight (Mw) of at least 30,000, an organohydrogenpolysiloxane having at least two silicon-bonded hydrogen atoms in one molecule, a white pigment, an inorganic filler other than the white pigment, a platinum metal-type catalyst, and a reaction inhibitor (refer to Kokai 2011-140550).
These compositions exhibit the following problems during transfer molding, injection molding, or compression molding: a low mold-filling performance, facile generation of voids and flashing, and/or a poor mold releasability; also, a slow curing rate and a poor workability in the molding operation. In addition, the cured products provided by the cure of these compositions, while offering the advantage of little heat- and/or light-induced discoloration, suffer from the problems of a large linear thermal expansion coefficient and/or a low mechanical strength at elevated temperatures, as well as the problems of an inadequate light reflectance and a large heat- and/or light-induced decline in mechanical strength.
It is an object of the present invention to provide a curable silicone composition that exhibits an excellent moldability and that forms a cured product that exhibits little heat- and/or light-induced discoloration, little heat- and/or light-induced decline in mechanical strength, a high light reflectance, and an excellent dimensional stability.
It is another object of the present invention to provide a cured product that exhibits little heat- and/or light-induced discoloration, little heat- and/or light-induced decline in mechanical strength, and a high light reflectance.
It is further another object of the present invention is to provide an optical semiconductor device that uses this cured product as a light-reflecting material.